A lateral impact protective device which comprises a head gas bag is disclosed in the patent publication WO 94/19215. The head gas bag described in this printed publication is designed in the form of a flexible hose and at its lateral ends is attached to the A-pillar and to the B-pillar. In the folded up condition, the gas bag extends under a covering along the A-pillar over the roof frame as far as the B-pillar. Since the gas bag is manufactured of a special purpose fabric, it's length is substantialy shortened during inflation. In the completely inflated state, the gas bag essentially extends linearly from the A-pillar as far as the B-pillar and prevents the head of a vehicle occupant striking the side window of the vehicle.